Only a minor proportion of patients with acute ischemic stroke receive treatment with intravenous thrombolysis. The purpose of this study was to explore reasons for not giving thrombolysis and to determine if there was a correlation between prehospital and in-hospital delay in a Norwegian ischemic stroke population. Patients with acute ischemic stroke were included during a 1-year period. Time intervals for prehospital and in-hospital delay, reasons for not treating with thrombolytic therapy in patients admitted within the time window and reasons for late arrival were recorded. In all, 290 patients were included, and 7.6 % were treated with intravenous thrombolysis. The most frequent reasons for not treating eligible patients were: minor symptoms (22.8 %), clinical improvement (17.5 %) and uncertainty about the diagnosis (12.3 %). Patients' reasons for delayed admission were: not attributing their symptoms to stroke (25.4 %), a wait-and-see attitude (25.4 %), and choosing to wait for the GP's office to open (14.3 %). Prehospital delay was strongly correlated to in-hospital delay (p < 0.001). In conclusion, a large percentage of patients with AIS are not treated with thrombolysis because of mild or rapidly improving symptoms, and because patients arrive too late to the hospital. Absolute and relative contraindications account for a minor proportion of reasons for excluding patients.